Forums

Incorrect behaviour with StringMaker inside IEnumerator

General discussion about Cobra. Releases and general news will also be posted here.
Feel free to ask questions or just say "Hello".

Incorrect behaviour with StringMaker inside IEnumerator

Postby Ourous » Wed Jun 24, 2015 3:51 pm

There seems to be incorrect behaviour in StringMaker.makeString when it is called from an IEnumerator that resolves inside a call to StringMaker.makeString. StringMaker._level is being set one-too-high during the calls from inside the IEnumerator, as it is being treated as an IEnumerable by the StringMaker.

Demonstrated here:
class Demo

def main

print .x
print .x.toList


def x as String*

print CobraImp._printStringMaker.level
print c'x'
print [1, 2, 3, 4].join('')

yield ''


Output:
Code: Select all
1
c'x'
'1234'
['']
0
x
1234
['']


EDITED OUT:

I originally had a proposed fix for this, but I've since realized it only covered some cases. When/if I can find a proper way to address this I will reply here.
Ourous
 
Posts: 10

Re: Incorrect behaviour with StringMaker inside IEnumerator

Postby Charles » Thu Jun 25, 2015 12:33 am

Yeah I've seen this problem and also had trouble formulating a fix.
Charles
 
Posts: 2515
Location: Los Angeles, CA

Re: Incorrect behaviour with StringMaker inside IEnumerator

Postby Ourous » Thu Jun 25, 2015 12:50 am

Found a fix for it. As well as .makeString counting String as an IEnumerable and incrementing _level, which is fixed too.

--removed, see below--
Last edited by Ourous on Sun Nov 15, 2015 9:20 pm, edited 2 times in total.
Ourous
 
Posts: 10

Re: Incorrect behaviour with StringMaker inside IEnumerator

Postby Ourous » Sun Nov 15, 2015 9:20 pm

StringMaker_fix_for_IEnumerator_V2.patch
(2.07 KiB) Downloaded 10985 times


Replacement for the patch. Fixes a cast exception that it introduced and adds tests.
Ourous
 
Posts: 10

Re: Incorrect behaviour with StringMaker inside IEnumerator

Postby Charles » Mon Nov 30, 2015 12:40 am

This is applied with a minor test case correction so that it passes on both .NET and Mono.

Thanks.
Charles
 
Posts: 2515
Location: Los Angeles, CA

Re: Incorrect behaviour with StringMaker inside IEnumerator

Postby james » Wed Dec 09, 2015 5:37 pm

Hi. Will this fix be available in the latest download? Thanks :)
james
 
Posts: 3

Re: Incorrect behaviour with StringMaker inside IEnumerator

Postby Ourous » Tue Dec 15, 2015 1:35 pm

The fix is applied to the latest revision (3119) if you install from source using a subversion client. It won't be in the 0.9.6 download file.
Ourous
 
Posts: 10

Re: Incorrect behaviour with StringMaker inside IEnumerator

Postby thriwkin » Wed Dec 16, 2015 2:34 am

How to install the latest version of the compiler from source?
See here: http://cobra-language.com/trac/cobra/wiki/HowToInstallFromSource


@ Ourous

Yes, the latest changeset (http://cobra-language.com/trac/cobra/changeset/3119)
does "fix" something:
- now the print statement can print an iterator that produces 1 element,
even if both, the iterator and the print statement, use the same instance of PrintStringMaker.

But what happens when the iterator produces more than 1 element?
Look at this example:

class Demo
def m1 as String*
"""
This is the iterator of the testcase, which was added to Cobra svn:3119.
It "enumerates" 1 item only.
"""
yield ['a', 'b', 'c'].join('')

def m3 as String*
"""
This is the same iterator, but it produces 3 items, instead of 1 only.
"""
yield ['a', 'b', 'c'].join('')
yield ['a', 'b', 'c'].join('')
yield ['a', 'b', 'c'].join('')

def main
print .m1
print .m3


The expected/correct output of print .m3 is:
- ['abc', 'abc', 'abc']
The actual output is
- in Cobra svn:3118: [''a''b''c'', ''a''b''c'', ''a''b''c''] -- all items wrong
- in Cobra svn:3119: ['abc', ''a''b''c'', ''a''b''c''] -- the first item is correct!

Ourous, you are right, it is the `_level` in `StringMaker.enumerableToString`:
it must be 0 when the `IEnumerator.moveNext` method of the iterator is executed -- but always, not just for the first item.
thriwkin
 
Posts: 26

Re: Incorrect behaviour with StringMaker inside IEnumerator

Postby Ourous » Wed Dec 30, 2015 3:44 pm

Ah damn I made a poor assumption - I figured that it resolved the entire enumerator into an enumerable when the first run through the for was executed. I'll get to work on this.

EDIT: Done

StringMaker_fix_for_IEnumerator_fix.patch
(393 Bytes) Downloaded 10712 times
Ourous
 
Posts: 10

Re: Incorrect behaviour with StringMaker inside IEnumerator

Postby EdwardMcIntosh » Mon Sep 03, 2018 1:51 pm

Howdy. Will this fix be accessible in the most recent download? Much appreciated :)
EdwardMcIntosh
 
Posts: 1

Next

Return to Discussion

Who is online

Users browsing this forum: No registered users and 82 guests

cron